Tsetse flies transmit the human and animal forms of African Trypanosomiasis, neglected diseases, which affect marginalized populations in sub-Saharan Africa. Control methods based upon pesticide-baited targets and traps can reduce tsetse populations, but have downsides, including environmental toxicity, collateral effects upon non- target organisms and high implementation cost. Thus, genetic and non-pesticide based vector control methods are desirable. This project will build the foundation for control methods that aim to reduce tsetse's reproductive capacity. We will investigate male accessory gland (MAGs) products, known as seminal fluid proteins (SFPs), which are transferred along with sperm to the female during mating. SFPs mediate important physiological and behavioral changes in mated female insects, including reduced receptivity to remating and increased oogenesis/egg deposition. Disruption/manipulation of SFP function(s) has the potential to reduce tsetse populations and hence disease transmission. Tsetse flies have a low reproductive capacity as they reproduce by obligate viviparity. Each gonotrophic cycle, females carry and nourish a single intrauterine offspring for the duration of its development. Females on average produce 8-10 offspring per lifetime. Our proposed studies are supported by the availability of 1) preliminary transcriptomic data on MAG gene expression in our target species Glossina morsitans morsitans (Gmm), 2) an annotated genome and extensive transcriptomic resources for Gmm, and 3) a large dataset of transcriptomes from other tsetse species. This study has 3 aims: 1. Identify putative SFP genes using transcriptomic, proteomic and genomic approaches, characterize their sex/tissue specificity, and examine temporal expression profiles during maturation and after mating. 2. Identify SFP orthologs and paralogs between multiple Glossina species by utilizing available transcriptomic and genomic resources, estimate sequence diversity of SFPs by polymorphism detection and identify conserved sex and tissue specific regulatory elements by in silico analysis. 3. Develop and apply gene silencing techniques to assess the functional role(s) of selected SFPs (~5) within the context of the tsetse reproductive fitness parameters.